My kids are at Larmenier. It's a great school - I have never regretted sending them there. I can't speak for St Mary's. It has always had a very good reputation, but I heard it had some staff changes a couple of years ago, and a few kids have since come over to Larmenier from there ( I don't know why - maybe for entirely different reasons). They're both good schools. I get the impression the intake is a bit different. Larmenier seems to attract more French and Italian parents.